Methods of making moisture-resistant downhole electrical feedthroughs

ABSTRACT

A method for making a downhole electrical feedthrough package where the feedthrough package may include a metal shell forming a shell conduit. A metal web may be coupled to the metal shell, and the metal web may form a web conduit. A conducting pin may extend through the shell conduit and web conduit. A dielectric seal may electrically isolate the conducting pin from the metal web. The dielectric seal may be formed by a bismuth glass based dielectric sealing material system having at least two of the four components selected from Bi2O3, B2O3, MO, and optionally REO forming a bismuth glass system. MO may be selected from ZnO, BaO, TiO2, and Fe2O3, and their glass making pre-cursors. REO may be selected from CeO2, Y2O3, Sc2O3, Nd2O3, Pr2O3, and lanthanum series oxides. One or more isolators may be disposed within the shell conduit proximate to the dielectric seal and surrounding a portion of the conducting pin.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending application Ser. No.15/592,725 filed May 11, 2017.

FIELD OF THE INVENTION

This patent specification relates to the high strength dielectricsealing material sealed electrical feedthrough package in general, andto the moisture-resistant dielectric sealing material sealed downholeelectrical feedthrough in particular for enabling downhole loggingtools, LWD and MWD tools reliable operation in water-based ormoisture-rich oil-based wellbores.

BACKGROUND

Electrical feedthroughs are used to connect an electrical power sourceto downhole logging tools and the like which determine physical,chemical, and structural properties of the formation. However, adownhole environment is subjected to a variety of harsh liquidenvironments such as brine, gas, and oil fluid that often contains waterand moisture. An electrical feedthrough typically comprises metalpin(s), sealed in an insulating material which may carry substantialamounts of power with signals up to a few thousand volts that requires ahigh insulation resistance. It is clear that if the moisture ispermitted to pass into the downhole logging tool enclosure due to failedhermetic seal of the feedthrough, it may lead to catastrophic electricalbreakdown.

Downhole logging tool and electrical circuits are packaged in ahermetically-sealed metal enclosure, which is either pressurized, orfilled with fluid, to protect the circuits from downhole corrosiveenvironment and humidity. The sealed tool enclosure uses an electricalfeedthrough that transmits the power to inside electronics or sends themeasured downhole data to surface instruments. For permanentinstallations in the downhole environment, it is important that theseelectrical feedthroughs are reliable. In particular, it is importantthat the downhole fluid is prevented downhole fluid and moisture frompenetrating the electrical feedthroughs because the presence of theconductive fluid, such as seawater or brine in the electricalfeedthroughs can cause a short circuit in the system. In one case, asealing material may be of high dielectric strength but lack ofmechanical strength and appropriate coefficient of thermal expansionthat may lead to sealing material cracks by high stress. In anothercase, a sealing material may be of high mechanical strength and amatched coefficient of thermal expansion to metal enclosure but lack ofsufficient electrical insulation to survive downhole temperature andpressure without failures. In also further case, a sealing material mayhave high dielectric and mechanical strength and also matchedcoefficient of thermal expansion to metal enclosure but lack of moistureresistance that could also lead to electrical breakdown by moisturedeteriorated electrical resistivity.

Aromatic polyether ketones (PEEK, PEK, PAEK, and PEKK) based organicpolymers are first type of dielectric sealing materials that widely usedin an electrical feedthrough seal for subsea and downhole logging tools.Typically, in low temperature installations, aromatic polyether ketonesbased polymer materials are used as the pressure barrier and insulatingcomponent. However, the structural integrity as well as the dielectricstrength of aromatic polyether ketones can be compromised at highertemperatures because of low glass transition temperature of T_(g)<150°C. Under long-term exposure to high pressure and temperature andcorrosive fluids and frequent thermal cycles during the deployment fromdownhole to surface, the hermetic seals will eventually fail, at leastallowing fluid and moisture to enter the pressure bulkhead and reach thecontact pins. If the invading fluid is conductive, which is usually thecase in downhole and subsea environments, a short circuit may occur inthe logging tool system, resulting in power and data loss. One the otherhand, although these thermoplastic materials have high dielectricstrength, their ambient water absorption of ˜0.5% could slowly degradedunder moisture-rich downhole or subsea environment, even withoutmoisture passing through the conducting pin surface.

Inorganic glasses and glass-ceramics (Corning 7070, 58061, EG2927,Li₂O—Al₂O₃—SiO₂, MgO—Al₂O₃—SiO₂, and ZnO—Al₂O₃—SiO₂ etc.) are secondtype of dielectric sealing materials that have high dielectric strength,electric resistivity, mechanical strength, and break-down voltage.Despite a great success in many glass-to-metal seal systems, these glassand glass-ceramic sealed electrical feedthroughs often failed not due tomechanical stress but due to the deterioration of the electricinsulation. One failure mode is that the sealing material is of ahydrophilic nature due to its porosity that leads to absorption ofmoisture or water and eventual short circuit. There is still a need fordeveloping a high moisture resistant dielectric sealing material sealedelectrical feedthrough that enables reliable operation under 30,000PSI/200° C. hostile water-based or moisture-rich downhole and subseaenvironments.

It is desirable for having a high mechanical strength and highdielectric strength with moisture-resistant dielectric sealing materialfor downhole electrical feedthrough package that not only provides highglass-to-metal seal strength against potential mechanical failures butalso provides high electrical insulation against potential electricalfailures even at moisture-rich downhole environment. The presentinvention relates to the high strength dielectric sealing materialsealed electrical feedthrough package in general, and to themoisture-resistant dielectric sealing material sealed downholeelectrical feedthrough in particular for enabling downhole loggingtools, LWD and MWD tools reliable operation in water-based ormoisture-rich oil-based wellbores.

BRIEF SUMMARY OF THE INVENTION

A downhole electrical feedthrough package, having a novelmoisture-resistant dielectric sealing material, and method for makingthe same are provided. In some embodiments, the feedthrough package mayinclude a metal shell forming a shell conduit. A metal web may becoupled to the metal shell, and the metal web may form a web conduit. Aconducting pin may extend through the shell conduit and web conduit. Adielectric seal may electrically isolate the conducting pin from themetal web. The dielectric seal may be formed by a bismuth glass baseddielectric sealing material system having at least two of the fourcomponents selected from Bi₂O₃, B₂O₃, MO, and optionally REO forming abismuth glass based dielectric sealing material system. A first isolatormay be disposed within the shell conduit proximate to a front side ofthe dielectric seal and surrounding a portion of the conducting pin, anda second isolator may be disposed within the shell conduit proximate toa rear side of the dielectric seal and surrounding a portion of theconducting pin.

According to another embodiment consistent with the principles of theinvention, a method of forming a downhole electrical feedthrough packagehaving a novel moisture-resistant dielectric sealing material isprovided. In some embodiments, the method may include the steps ofcombining at least two of the four components selected from Bi₂O₃, B₂O₃,MO, and optionally REO to form a glass mixture; heating the glassmixture to approximately 650 to 1400° C.; quenching the heated glassmixture in de-ionized water bath to form glass frits; sintering theglass frits with hollow cylinder shape and fitted into a conduit of ametal shell to form an electrical feedthrough assembly; firing theelectrical feedthrough assembly at first temperature (T₁) for a firsttime period to form a dielectric seal and to provide a first thermalenergy to the dielectric seal; heating the electrical feedthroughassembly at second temperature (T₂) for a second time period to providea second thermal energy to the dielectric seal; cooling the dielectricseal of the electrical feedthrough assembly to ambient temperature for athird time period; and integrating two isolators into the conduit sothat the dielectric seal is in contact with at least one of theisolators.

In further embodiments, the bismuth glass based dielectric sealingmaterial system may comprise binary Bi₂O₃-MO compositions, in which MOmay be selected from the ZnO, BaO, TiO₂, and Fe₂O₃, and their glassmaking pre-cursors.

In further embodiments, the bismuth glass based dielectric sealingmaterial system may comprise ternary Bi₂O₃—B₂O₃-MO compositions, inwhich MO may be selected from the group consisting of ZnO, BaO, TiO₂,Fe₂O₃, and their glass making pre-cursors.

In further embodiments, the bismuth glass based dielectric sealingmaterial system may comprise quaternary Bi₂O₃—B₂O₃-MO-REO compositions,in which MO may be selected from ZnO, BaO, TiO₂, Fe₂O₃, and their glassmaking precursors, and REO may be selected from CeO₂, Y₂O₃, Sc₂O₃,Nd₂O₃, Pr₂O₃, and lanthanum series oxides.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the present invention are illustrated as an exampleand are not limited by the figures of the accompanying drawings, inwhich like references may indicate similar elements and in which:

FIG. 1A depicts a sectional view of an example of an electricalfeedthrough comprising a high moisture-resistant dielectric sealingmaterial according to various embodiments described herein.

FIG. 1B shows a sectional view of an example of a downhole electricalfeedthrough without dielectric material to illustrate the relationshipbetween the shell conduit and web conduits disposed in the metal shellaccording to various embodiments described herein.

FIG. 2 illustrates a sectional view of another example of a downholeelectrical feedthrough comprising a high moisture-resistant dielectricsealing material according to various embodiments described herein.

FIG. 3 depicts a triangulation phase diagram for making exemplary highmoisture-resistant dielectric sealing materials according to variousembodiments described herein.

FIG. 4 illustrates another triangulation phase diagram for makingfurther exemplary high moisture-resistant dielectric sealing materialsaccording to various embodiments described herein.

FIG. 5A shows an example glass-to-metal sealing body fabrication processby referencing polymorphs of Bi₂O₃ dominated glass-ceramic materialaccording to various embodiments described herein.

FIG. 5B shows another example glass-to-metal sealing body fabricationprocess by referencing polymorphs of Bi₂O₃ dominated glass-ceramicmaterial according to various embodiments described herein.

FIG. 6 shows the measured electrical resistivities of two exemplaryternary Bi₂O₃—B₂O₃—ZnO sealing materials with 570 degrees Celsius and530 degrees Celsius firing temperatures

FIG. 7 depicts a graphical representation of the mechanical compressionfrom four exemplary dielectric sealing material sealed downholeelectrical feedthroughs according to various embodiments describedherein.

FIG. 8 illustrates a graphical representation of thetemperature-dependent insulation resistances from three exemplarydielectric sealing material sealed downhole electrical feedthroughsaccording to various embodiments described herein.

FIG. 9 shows a graphical representation of the volumetric resistivityand maximum operating temperatures from resistances from three exemplarydielectric sealing material sealed downhole electrical feedthroughsaccording to various embodiments described herein.

FIG. 10 depicts a graph showing typical effective insulation resistancemeasurements from three example moisture-sensitive dielectric sealingmaterial sealed based electrical feedthrough packages subsequent tosoaking in 100 degrees Celsius water for 1-2 hours duration.

FIG. 11 illustrates a graph showing measured effective insulationresistance values from three example moisture-resistant dielectricsealing material sealed electrical feedthrough packages subsequent tosoaking in 100 degrees Celsius water for 1-2 hours duration.

FIG. 12 depicts a graph showing measured insulation resistances fromfour exemplary sealing material based feedthrough prototypes, after 24hours at 30,000 PSI water-based hydraulic pressurized soaking process.

FIG. 13 shows a block diagram of an example method of forming a downholeelectrical feedthrough package according to various embodimentsdescribed herein.

DETAILED DESCRIPTION OF THE INVENTION

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items. As used herein, the singularforms “a,” “an,” and “the” are intended to include the plural forms aswell as the singular forms, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, steps, operations, elements, and/orcomponents, but do not preclude the presence or addition of one or moreother features, steps, operations, elements, components, and/or groupsthereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by onehaving ordinary skill in the art to which this invention belongs. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure and will not be interpreted in an idealized or overlyformal sense unless expressly so defined herein.

In this invention, the glass compositions and the method of manufactureof glass compositions describe the mixing of oxides to create theresultant glass composition. It will be understood that many othercompounds, other than the oxides mentioned, and the pure elements can beused as glass making precursors to create the resultant desired glasscomposition. For example, if the bismuth oxide is a component of theglass, bismuth, bismuth carbonate, bismuth nitrate, bismuth hydroxide,bismuth ammoniate, bismuth hydride, or any other similar bismuthcompound, either singularly, or in any combination, can be used asprecursors to create the resultant desired glass composition.Accordingly, for the sake of clarity, this description will refrain fromrepeating every possible combination of the glass making precursors inan unnecessary fashion. Nevertheless, the specification and claimsshould be read with the understanding that such combinations areentirely within the scope of the invention and the claims.

In describing the invention, it will be understood that a number oftechniques and steps are disclosed. Each of these has individual benefitand each can also be used in conjunction with one or more, or in somecases all, of the other disclosed techniques. Accordingly, for the sakeof clarity, this description will refrain from repeating every possiblecombination of the individual steps in an unnecessary fashion.Nevertheless, the specification and claims should be read with theunderstanding that such combinations are entirely within the scope ofthe invention and the claims.

For purposes of description herein, the terms “upper”, “lower”, “left”,“right”, “rear”, “front”, “side”, “vertical”, “horizontal”, andderivatives thereof shall relate to the invention as oriented in FIG. 1.However, one will understand that the invention may assume variousalternative orientations and step sequences, except where expresslyspecified to the contrary. Therefore, the specific devices and processesillustrated in the attached drawings, and described in the followingspecification, are simply exemplary embodiments of the inventiveconcepts defined in the appended claims. Hence, specific dimensions andother physical characteristics relating to the embodiments disclosedherein are not to be considered as limiting, unless the claims expresslystate otherwise.

Although the terms “first”, “second”, etc. are used herein to describevarious elements, these elements should not be limited by these terms.These terms are only used to distinguish one element from anotherelement. For example, the first element may be designated as the secondelement, and the second element may be likewise designated as the firstelement without departing from the scope of the invention.

As used in this application, the term “about” or “approximately” refersto a range of values within plus or minus 10% of the specified number.Additionally, as used in this application, the term “substantially”means that the actual value is within about 10% of the actual desiredvalue, particularly within about 5% of the actual desired value andespecially within about 1% of the actual desired value of any variable,element or limit set forth herein.

In some embodiments, a surface or element may be positioned proximate toanother surface or element so that the two surfaces or elements are incontact with each other. In other embodiments, a surface or element maybe positioned proximate to another surface so that the two surfaces orelement are not in contact with each other but are between 0.0001 to10.0 millimeters from each other.

New high dielectric strength with moisture-resistant dielectric sealingmaterial sealed electrical feedthroughs and methods are discussedherein. In the following description, for purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be evident, however, toone skilled in the art that the present invention may be practicedwithout these specific details.

The present disclosure is to be considered as an exemplification of theinvention, and is not intended to limit the invention to the specificembodiments illustrated by the figures or description below.

The present invention will now be described by example and throughreferencing the appended figures representing preferred and alternativeembodiments. FIGS. 1A, 1B, and 2 illustrate examples of a downholeelectrical feedthrough (“the feedthrough”) 100 according to variousembodiments. In some embodiments, the feedthrough 100 may comprise ametal shell 11 forming a shell conduit 12. A metal web 41 may be coupledto the metal shell 11 within the shell conduit 12, and the metal web 41may form one or more web conduits 42. One or more conducting pins 13 mayextend through the shell conduit 12 and through a web conduit 42. One ormore dielectric seals 21, 26, may also be disposed in the conduit 12,and each dielectric seal 21, 26, may electrically isolate one or moreconducting pins 13 from the metal web 41. One or more isolators 31, 36,may also be disposed within the conduit 12, and each isolator 31, 36,may surround a portion of each conducting pin 13 disposed in the conduit12 and electrically isolate the one or more conducting pins 13 from themetal shell 11. Each isolator 31, 36, may be positioned in contact witha dielectric seal 21, 26, thereby forming a vibration dampening junction24, 29, at the interface of an isolator 31, 36, with a dielectric seal21, 26. Optionally, the feedthrough 100 may comprise one or more ceramicsleeves 51 which may be disposed in the web conduit 42, and each ceramicsleeve 51 may also electrically isolate one or more conducting pins 13from a portion of the metal web 41.

Referring to the example shown in FIG. 1A, in some embodiments, afeedthrough 100 may be configured as a single-directional connectorsuitable for enduring hydraulic pressure 79 from the front end 71. Thefeedthrough 100 may comprise one or more, such as seven, conducting pins13 which may be extend through the conduits 12, 42. A portion of eachconducting pin 13 may be surrounded by a dielectric seal 21, and eachdielectric seal 21 may electrically isolate its respective conductingpin 13 from all or a portion of the metal web 41. A first isolator 31may be disposed within a conduit 12, and the first isolator 31 maysurround a portion of each conducting pin 13 disposed in the conduit 12proximate to the front end 71. The first isolator 31 may be positionedin contact with the surface of the dielectric seals 21 that is facingthe front end 71 thereby forming a first vibration dampening junction 24at the interface of each dielectric seal 21 with the first isolator 31.A second isolator 36 may also be disposed within the conduit 12, and thesecond isolator 36 may surround a portion of each conducting pin 13disposed in the conduit 12 proximate to the rear end 72. In someembodiments, the metal shell 11 may comprise or be made from titaniumalloys, stainless steel alloys, Nitronic alloys, Inconel alloys, and anyother metal alloys preferably with a minimum chromium contentsubstantially of 10.5%.

In some embodiments, dielectric seals 21 which may insulate theconducting pins 13 from all or portions of the metal web 41 may bepositioned centrally within a web conduit 42. In some embodiments, thefeedthrough 100 may comprise a flange 16 which may be positionedsubstantially centrally on the outer surface 17 of the metal shell 11and dielectric seals 21 which may insulate the conducting pins 13 fromthe metal web 41 may be positioned centrally within the web conduit 42.In other embodiments, and as shown in FIG. 1, a flange 16 may bepositioned substantially centrally on the metal shell 11 and dielectricseals 21 which may insulate the conducting pins 13 from the metal web 41may be positioned closer to one end 71, 72, such as closer to the rearend 72, that is to be subjected to hydraulic pressure. In furtherembodiments, the isolators 31, 36, may be substantially the same size,while in other embodiments, one isolator 31, 36, such as the isolator 36that is to be subjected to hydraulic pressure 79, may be smaller thanthe other isolator 31.

Turning now to the example shown in FIG. 2, in some embodiments, afeedthrough 100 may be configured as a bi-directional connector suitablefor enduring hydraulic pressure 79 to both ends 71, 72. The feedthrough100 may comprise one or more, such as seven, conducting pins 13 whichmay be extend through the conduits 12, 42. A portion of each conductingpin 13 may be surrounded by a ceramic sleeve 51, and each ceramic sleeve51 may electrically isolate its respective conducting pin 13 from aportion of the metal web 41. A portion of each conducting pin 13 mayalso be surrounded by a first dielectric seal 21, and each firstdielectric seal 21 may electrically isolate its respective conductingpin 13 from a portion of the metal web 41. A portion of each conductingpin 13 may also be surrounded by a second dielectric seal 26, and eachsecond dielectric seal 26 may electrically isolate its respectiveconducting pin 13 from a portion of the metal web 41. A first isolator31 may be disposed within the conduit 12, and the first isolator 31 maysurround a portion of each conducting pin 13 disposed in the conduit 12proximate to the front end 71. The first isolator 31 may be positionedproximate or in contact with the surface of each of the first dielectricseals 21 that is facing the first end 71 thereby forming a firstvibration dampening junction 24 at the interface of each firstdielectric seal 21 with the first isolator 31. A second isolator 36 mayalso be disposed within the conduit 12, and the second isolator 36 maysurround a portion of each conducting pin 13 disposed in the conduit 12proximate to the rear end 72. The second isolator 36 may be positionedproximate or in contact with the surface of each of the seconddielectric seals 26 that is facing the rear end 72 thereby forming asecond vibration dampening junction 29 at the interface of each seconddielectric seal 26 with the second isolator 36. In further embodiments,a ceramic sleeve 51 may comprise or be formed from any fine ceramics(also known as “advanced ceramics”) that do not conduct electricity andwhich preferably have resistance to acid, alkali, organic solvents,and/or water, including higher strength ceramic material such as azirconia, alumina, and steatites.

The feedthrough 100 may comprise one or more conducting pins 13 whichmay be used to conduct electricity through the feedthrough 100. Aconducting pin 13 may comprise an electrically conductive material whichmay be used to communicate electricity through the conduit of thefeedthrough 100. In some embodiments, a conducting pin 13 may be madefrom titanium alloys, copper alloys, Beryllium copper (BeCu) alloys,chromium copper (CrCu) alloys, Brass, Inconel alloys, Alloy 52, othernickel-iron alloys, Kovar alloy, and other nickel-cobalt ferrous alloys.In other embodiments, a conducting pin 13 may be made from or compriseany other electrically conductive material.

An isolator 31, 36, may comprise an electrically non-conductive materialwhich may be used to prevent the communication of electricity throughthe entire length of the conduit or through the metal shell 11 of thefeedthrough 100. In some embodiments, an isolator 31, 36, may be madefrom or comprise thermoplastic aromatic polyether ketones, such aspolyamide-imide (PAI), polyether ether ketone (PEEK), PolyEtherKetone(PEK), polyaryletherketone (PAEK), and Polyetherketoneketone(PEKK),based organic polymers. In preferred embodiments, an isolator 31, 36,may be made from or comprise high-temperature PAI or glass-reinforcedPAI thermoplastic material. In further embodiments, an isolator 31, 36,may be made from or comprise a PAI thermoplastic and a PEEKthermoplastic. In alternative embodiments, isolator 31, 36, may be madefrom or comprise any engineered polymer with high-temperature (greaterthan 220 degrees Celsius) and high compression strength (greater than180 kPa). On the other hand, these isolators 31, 36, may be used as avibration damper against unexpected mechanical shock especially duringinstallation process or operation in the lateral or horizontal wells, orreduce package deformation that frequently causes glass cracks in theglass-to-metal (dielectric seal 21, 26, to metal web 41 or metal shell11) sealing body. Additionally, isolators 31, 36, may function also as amechanical seal in the feedthrough 100 to block potential downhole fluidleaked from a failed mechanical seal, such as threading 14 or exteriorseals 15, from contacting a glass-to-metal sealing body. Since a PAI orPEEK based thermoplastic polymer has high continuous operationtemperature of 260° C., it may be used in isolators 31, 36, forlong-term downhole operation.

A dielectric seal 21, 26, may comprise an electrically non-conductivematerial which may be used to prevent the communication of electricitythrough the entire length of the conduit or through the metal shell 11of the feedthrough 100. Generally, “sealing material” or “dielectricsealing material” may refer to the material as dielectric seal 21, 26,may be formed with high mechanical strength and dielectric strength ingeneral. A dielectric seal 21, 26, may also preferably be made from orcomprise glass or glass-ceramic that has not only high mechanicalstrength and dielectric strength but also has high moisture resistancefor HPHT downhole environmental deployment. Thermoplastic PEEK basedsealing material could provide acceptable mechanical strength, highdielectric strength but it still has low water absorption of ˜0.5% evenat ambient condition (immersion PEEK in water at 23 degrees Celsius for24 hrs, see ASTM D570), which is undesirable for long-term being used inwater-based or moisture-rich downhole and subsea.

In some embodiments, the dielectric seal 21, 26, may be made from abismuth glass based dielectric sealing material system. A bismuth glassbased dielectric sealing material system may be or comprise a binarydielectric bismuth glass system, or a ternary dielectric bismuth glasssystem, or a quaternary dielectric bismuth glass system. A binarydielectric bismuth glass system may comprise Bi₂O₃-MO with MO=ZnO, BaO,TiO₂, Fe₂O₃. A ternary dielectric bismuth glass system may compriseB₂O₃—Bi₂O₃-MO with MO=ZnO, BaO, TiO₂, Fe₂O₃.

In more specific embodiments, the dielectric seal 21, 26, may be madefrom a bismuth glass based dielectric sealing material system. A bismuthglass based dielectric sealing material system may be or comprise aquaternary dielectric bismuth glass system comprising B₂O₃—Bi₂O₃-MO-REOwith MO=ZnO, BaO, TiO₂, Fe₂O₃ and REO=lanthanum series based rare earthoxide oxides (REO) in which the REO enhanced the moisture resistance byincreased hydrophobicity of the glass system. The use of REO in theglass system enhances the moisture resistance of the glass system basedon the REO in inhibiting hydrogen bonding with interfacial watermolecules resulting in a hydrophobic hydration structure. In fact, theREO has a low surface fee energy that water will bead up at its surface,which makes them attractive for repelling water or conductive scalingand fouling onto the sealing material surface.

In some embodiments, a dielectric bismuth glass system may comprise B₂O₃between 0 mol % and 40 mol %. In some embodiments, a dielectric bismuthglass system may comprise REO between 0 mol % and 15 mol %. In someembodiments, a dielectric bismuth glass system may comprise MO between 0mol % and 35 mol %. In some embodiments, a dielectric bismuth glasssystem may comprise Bi₂O₃ between 20 mol % and 60 mol %. In someembodiments, a dielectric bismuth glass system may comprise a glasstransition temperature of approximately from 350 C to 480 C, coefficientof thermal expansion from 8.0 10-6 m/m K to 12 10-6 m/m K, Young'smodulus from 50 GPa to 65 GPa, a mass density of approximately from 5.5g/cm3 to about 7.0 g/cm3, and resistivity from 1.0×10¹¹ Ω-cm to 1.0×10¹⁴Ω-cm.

To make up above binary, ternary and quaternary bismuth sealing glasssystems, FIG. 3 has provided a glass system composition triangulationphase diagram for explaining how to obtain exemplary dielectric sealingmaterials having high electrical resistivity and hydrophobicity to beused as a dielectric seal 21, 26. The glass system compositions may bebased on glass former(s) and network modifier(s) with variedcompositions thereby forming different glass system materials. Bi₂O₃acts as both glass-network former with [BiO₃] pyramidal units and asmodifier with [BiO₆] octahedral units. As shown in Table 1, sixexemplary dielectric sealing materials (A, B, C, D, E, and F) arecomposed of the 5-24 mol % MO, 20-46 mol % B₂O₃, 40-55 mol % Bi₂O₃, and0-7 mol % Rare earth oxide (REO), as a specific example, the Ceriumoxide (CeO) is used. In other embodiments, dielectric sealing materialsare composed of the 0-35 mol % MO (MO=ZnO, BaO, Fe₂O₃, TiO₂ etc.), 0-40mol % B₂O₃, 20-60 mol % Bi₂O₃, and 0-10 mol % Rare earth oxide (REO).

TABLE 1 Composition of six exemplary glass materials for making highstrength moisture-resistant dielectric sealing materials MO Bi₂O₃ B₂O₃REO Sample (mol %) (mol %) (mol %) (mol %) A 12 42 40 6 B 5 42 46 7 C 555 36 4 D 24 54 20 2 E 24 40 32 4 F 20 40 40 0

The triangulation diagram of FIG. 3 with primary Bi₂O₃, B₂O₃, ZnO orBaO, can be used to find approximate composition for the synthesizeddielectric sealing material performance in both mechanical anddielectric properties. As a fact that the down selection of amoisture-resistant sealing material could be a binary glass system (forexample, Bi₂O₃—ZnO), a ternary system (for example, Bi₂O₃—B₂O₃-MO,MO=ZnO, BaO, Fe₂O₃, TiO₂ etc.), and quaternary system (for example,Bi₂O₃—B₂O₃—ZnO-REO). The quaternary B₂O₃—Bi₂O₃-MO-REO based dielectricsealing materials have shown glass transition temperature from 400 to480° C., but decreasing with the increasing of Bi₂O₃/B₂O₃ ratio, andincreasing with the increasing of ZnO/B₂O₃ ratio and BaO/B₂O₃ ratio. Thecoefficient of thermal expansion could be from 7.0 to 12.0×10⁻⁶ m/m·°C., with values increasing with increasing Bi₂O₃/B₂O₃, ZnO/B₂O₃ ratio orBaO/B₂O₃ ratio. The ambient effective insulation resistance is from1×10¹³ to 1×10¹⁵ Ω, with its coefficient of insulation resistance rangesfrom—(0.05±0.01) 1/° C. from 100° C. to 400° C. Thus, the down selectionof a glass system composition will greatly determine thermal, physicaland mechanical properties of the dielectric sealing material.

FIG. 4 has provided a glass system composition triangulation phasediagram for obtaining further exemplary dielectric sealing materialshaving high electrical resistivity and hydrophobicity to be used to forma dielectric seal 21, 26. The glass system compositions may have waterinsoluble glass former(s) and network modifier(s) with variedcompositions thereby forming different glass system materials. However,the rare earth oxide, such as cerium oxide, has relative highcomposition of 9-14%, twice that of the sealing materials in Table1/FIG. 3. As shown in Table 2, a second set of six synthesized sealingmaterials (G, H, J, K, L, and M) are composed of the 4-21 mol % MO (ZnOor BaO), 15-35 mol % B₂O₃, 46-57 mol % Bi₂O₃, and 0-14 mol % Ceriumoxides. In other embodiments, bismuth glass based dielectric sealingmaterials may be composed of the 0-25 mol % MO (MO=ZnO, BaO, Fe₂O₃, TiO₂etc.), 0-40 mol % B₂O₃, 40-60 mol % Bi₂O₃, and 0-15 mol % Rare earthoxide (REO).

TABLE 2 Composition of six further exemplary glass materials for makinghigh strength moisture-resistant dielectric sealing materials MO Bi₂O₃B₂O₃ REO Sample (mol %) (mol %) (mol %) (mol %) G 11 47 31 11 H 4 47 3514 J 4 57 28 11 K 20 56 15 9 L 17 46 28 9 M 20 45 35 0

These quaternary B₂O₃—Bi₂O₃-MO-REO based dielectric sealing materialsmay be prepared by conventional melt-quench technique using reagentgrade chemicals Bi₂O₃, B(OH)₃, ZnO, or BaO, and CeO. Initial rawmaterial powders may be weighed to the appropriate amounts, mixedtogether in a container, then, transferred to a platinum crucible. Theplatinum crucible may be heated in an electrically heated furnace, orother heating method, to a temperature of about 850° C. depending on thecomposition. The crucible may be placed in furnace and allows themelting for the desired time in which the glass could be melt properlywithout any un-melted element left behind. After allowing sufficientmelting temperature, melting time and intermittent stirring to the melt,the melt may then be caste on a container filled with ambienttemperature de-ionized water. The obtained glass frits may be ground tohave a particle size preferably of 2-10 μm for making hollow cylindershaped beads, following a high compression process optionally using aburn-off polymer binder. This embodiment and other embodiments describedherein are not limited by the above sealing material making method. Infact the sealing glasses may be made from bismuth oxide that is acomponent of the glass, bismuth, bismuth carbonate, bismuth nitrate,bismuth hydroxide, bismuth ammoniate, bismuth hydride, or any othersimilar bismuth compound, either singularly, or in any combination, usedas precursors to create the resultant desired glass composition,following a similar preparation process described as above.

To obtain appropriate mechanical and thermal properties from asynthesized sealing material the mass density of such a quaternary glasssystem depends upon ratio of each composition over glass system. Theeffective density can be approximately written by:

ρ=Σ_(n=1) ^(k)=α_(n)·ρ_(n) and Σ_(n=1) ^(k)α_(n)=1  (1)

where α_(n) and ρ_(n) are fraction and mass density of each glasscomposition, and k represents the number of compositions in thesynthesized glass system. If starting from an initial density, ρ_(o), ofthe simple glass system, such as only Bi₂O₃, the incorporation ofdifferent glass compositions, such as B₂O₃, ZnO, BaO, and CeO, thedensity variation in the dielectric sealing material could lead to acorresponding variation in the effective coefficient of thermalexpansion (CTE) by

$\begin{matrix}{{CTE} = {\frac{\Delta \; V}{\left( {T_{g} - T} \right)V_{o}} = {- \frac{\rho - \rho_{o}}{\left( {T_{g} - T_{o}} \right)\rho}}}} & (2)\end{matrix}$

where the CTE is determined by the sealing material volume or densitychange, T_(g) is glass transition temperature. It is clear that theincorporation of low density glass compositions will increase CTE of thesynthesized glass system. For example, the initial density of Bi₂O₃,B₂O₃, and ZnO in the ternary glass system of B₂O₃—Bi₂O₃—ZnO is 8.90,2.55, and 5.61 g/cm³, respectively. The effective mass density willdepend upon either mol percentage or weight percentage of each chemicalcomponent. The increase of the B₂O₃ composition could effectively reduceeffective mass density, but inversely increase CTE.

Conventional ceramic materials may have either crystalline (includingsemi-crystalline and polycrystalline, nanocrystalline, andmicrocrystalline) structure or an amorphous structure. Crystallinematerials may have different phases at different temperature and/orpressure conditions, and may exhibit reversible phase transitions atdifferent temperatures and pressures. An amorphous material may have nophase transition but instead a series of morphology variation, namely, avariation from one morphology to another, where sometimes this variationis irreversible (for example, a relatively looser materialmicrostructural morphology may be able to transition to a more condensedmorphology, but this transition may not be reversible). Normally, aceramic material may have mixed phases or polymorphs that modulatemechanical and dielectric strengths of the dielectric sealing material.For fabricating such a bismuth oxide contained dielectric sealingmaterial, both the firing temperature and isothermal heating time arecritical for obtaining a stable material microstructure or crystallinephase with preferred dielectric and mechanical strengths.

To better understand sealing material microstructures and phases it willbe helpful by understanding Bi₂O₃ glass material first because of itsmulti-phase characters or five polymorphic forms for pressure less than50,000 PSI. Two stable polymorphs, namely monoclinic α phase andface-centered cubic δ phase. There are three metastable phases, namely,tetrahedral β phase, body-centered-cubic γ phase and triclinic co phase.FIGS. 5A and 5B illustrate quaternary B₂O₃—Bi₂O₃-MO-REO based dielectricsealing materials that may also have similar several polymorphs as Bi₂O₃glass. For example, at ambient Bi₂O₃ glass has a monoclinic crystalα-phase structure. While at temperature of 500-650 degrees Celsius Bi₂O₃has a structure related to Bi₁₂SiO20 bcc γ-phase structures. Attemperature of 650-730 degrees Celsius fcc δ-phase Bi₂O₃ is principallyan ionic conductor with a defective fluorite-type crystal structure. Thesealing material has to be one of stable polymorphs, either themonoclinic α phase or δ phases. During glass firing process the initialsintered glass frits will be fired at a certain temperature that theglass structure may transforms to the cubic δ-Bi₂O₃ if it is heatedabove 730 degrees Celsius, until melting at 820-860 degrees Celsius. Themicrostructure of Bi₂O₃ during cooling process will be transformed fromthe δ-phase to tetragonal β-phase or γ-phase, then to α-phase or withmulti-phase microstructures, depending upon the cooling process. On theother hand, on cooling δ-Bi₂O₃ process it is possible to form twointermediate metastable phases at ambient conditions: the tetragonal βphase (SG P-421c, No. 114), also known as sphaerobismoite, at ˜650degrees Celsius, and the body-centered cubic γ phase (SG I23, No. 197)at ˜640 degrees Celsius The γ-phase can exist at room temperature withvery slow cooling rates, but α-phase Bi₂O₃ always forms on cooling theβ-phase. The α-phase exhibits p-type electronic conductivity at roomtemperature which transforms to n-type conductivity (charge is carriedby electrons) between 550 degrees Celsius and 650 degrees Celsius,depending on the oxygen partial pressure. The conductivity in the β, γand δ-phase is predominantly ionic with oxide ions being the main chargecarrier. The conductivity (resistivity) of δ-Bi₂O₃ is about three ordersof magnitude greater (lower) than monoclinic α phase. For obtaining adesirable sealing material with high dielectric strength, it is criticalto control crystalline phase by firing temperature and heating duration,as well as the cooling process.

By referencing the phase diagram in the Bi₂O₃ glass as shown in FIGS. 5Aand 5B, a firing processes for making stable dielectric sealingmaterials having high electrical resistivity and hydrophobicity isdepicted. FIG. 5A illustrates a graphical representation of how abinary, ternary or a quaternary dielectric sealing material system maybe fired at relative high temperature. In some embodiments, afabricating process may begin with heating up the metal shell 11 havingconducting pin(s) 13 and sealing material disposed within the conduit 12at a first temperature (T₁) between 300 degrees Celsius and 400 degreesCelsius for a first time period (τ₁) or duration of 10 to 30 minutes.Next, the furnace temperature may be increased from T₁ to secondtemperature (T₂) between 550 degrees Celsius and 650 degrees Celsius andmaintained at T₂ for a second time period (τ₂) or duration of 30 to 45minutes. Next, the whole assembly may be cooled down to ambient. A fastquenching process could make amorphous glass dominated multi-phasedielectric sealing material. However, a cooling process with slow ratemay form α-phase dominated multi-phase sealing material with a smallportion of the δ-phase microstructures.

FIG. 5B depicts a graphical representation of another fabricationprocess for making quaternary B₂O₃—Bi₂O₃-MO-REO based α-phase dominateddielectric sealing material. In some embodiments, the process maycomprise firing the initial glass-to-metal seal assembly at a mediumtemperature whenever the rare earth oxide has relative lower compositionfor making stable glass network. In some embodiments, a fabricatingprocess may begin with heating up the metal shell 11 having conductingpin(s) 13 and sealing material disposed within the conduit 12 at a firsttemperature (T₁) between 300 degrees Celsius and 400 degrees Celsius fora first time period (τ₁) or duration of 10 to 30 minutes. Next, thefurnace temperature may be increased from T₁ to second temperature (T₂)between 480 degrees Celsius and 550 degrees Celsius and maintained at T₂for a second time period (τ₂) or duration of 30 to 45 minutes. Next, thewhole assembly may be cooled down to ambient also by either quenchingprocess or slow cooling process. A fast quenching process could alsomake glass-ceramic dielectric sealing material, which may be composed ofamorphous glass network and monoclinic α-phase grinds. However, a slowcooling process may be possible to make monoclinic α-phase dominatedsealing material.

As mentioned, an aspect of the quenching process can be described bythermal tempering process that is the use of a quenching fluid (such aswater, hydrocarbon or mineral oil, or gas/liquid air and nitrogen)having an appropriate thermal conductivity, density, viscosity andspecific heat capacity. To efficiently dissipate the heat generated bythe quenching process to create a desirable material microstructure thebaseline temperature and thermal conductivity of the quenching mediumshould be considered. A low-temperature baseline enables a relativelyhigh cooling rate, such as might be achieved by quenching using a liquidnitrogen medium. A high-temperature quenching fluid could slow down thecooling rate, such as quenching a metal in a hot fluid (boiling water,hot oil), but the microstructure,

, of the sealing material having the preferred crystalline phase ormaterial properties will depend upon both the cooling rate and thethermal conductivity difference between the quenching fluid and thesealing glass, as described by:

Q∝η(T _(g) −T)/(k−k _(g)),  (3)

where k is thermal conductivity of the quenching fluid, and k_(g)(˜1.0W/m/K) is the thermal conductivity of the sealing material, and η iscooling rate. From thermal conductivity of the quenching fluid, such asAir, N₂ or O₂, the quenching rate, η, will be critical factor incontrolling the phase or microstructure of the sealing material.

In some embodiments, the method to obtain α-phase dominated sealingmaterial is by a combined firing temperature and cooling processcontrol. FIG. 6 has shown an exemplary data from a ternaryB₂O₃—Bi₂O₃—ZnO based dielectric sealing material, which is measured fromtwo different firing temperatures but following a slow cooling process.The insulation resistance of α-phase like sealing material may be around0.60×10¹⁴ Ω-cm, but that of the α and δ mixed phase like sealingmaterial is only about 2.5×10¹¹ Ω-cm, which is close to about 2-3 orderslow in amplitude than α-phase like sealing material.

To demonstrate if these fabricated sealing materials have appropriatemechanical and dielectric strengths several electrical feedthroughprototypes have been made based on Inconel 718 metal shell 11 andInconel X750 conducting pin 13. In preferred embodiments, an electricalfeedthrough 100 may use CTE mismatched compression method to integratedielectric sealing material with Inconel metal shell 11 and conductingpin(s) 13 together as a hermetically sealed feedthrough 100 formechanical and electrical quantification tests. The typical outerdiameter of a metal shell 11 may be approximately 4.06 mm with the shellconduit 12 having a diameter of approximately 1.98 mm with an overalllength of 6.66 mm although the feedthrough 100 may be configured withany other dimensions. Four glass systems have been used to make theseprototypes, where A is Bi₂O₃—B₂O₃—Zn, B is Bi₂O₃—B₂O₃-MO-REO, C isPbO—B₂O₃—SiO₂—TiO₂, and D from a ternary B₂O₃—SiO₂—SrO glass system.FIG. 7 has illustrated the internal compression stress on the metalshell 11 as a function of the downhole temperature. Obviously, thisthermo-mechanical stress has high amplitude at low temperature and theelevated temperature actually releases compression. By comparing highcompression strength (−400 MPa to −500 MPa) of these sealing materials,the ratio of this stress amplitude over compression strength is about 2to 3 for possible operation range from −40 degrees Celsius to 300degrees Celsius. Despite the hydraulic pressure also adding about 10%compression stress onto the metal shell 11 outer surface 17, the 2-3ratios are acceptable mechanical strength for downhole deployment.However, the true maximum operation temperature actually also dependsupon electrical insulation. FIG. 8 has given the measuredtemperature-dependent insulation resistance, or temperature-dependenthot IR, from exemplary A, B, and C sealing glass material sealedelectrical feedthrough 100 prototypes.

As a fact that moisture could be evaporated whenever the temperature ishigher than 85 degrees Celsius and the obtained insulation resistance isdefined as volumetric resistance, R_(v), which is described by

$\begin{matrix}{{R_{v} = \frac{\rho \left( {\frac{\varphi_{g}}{\varphi_{p}} - 1} \right)}{2\pi \; L}},} & (4)\end{matrix}$

where ρ is resistivity Ω-cm, L is sealing length, φ_(g) and φ_(p) isouter and inner diameter of the sealing glass hollow cylinder,respectively. Obviously, the higher the resistivity is, the higher theinsulation resistance is for a dielectric sealing material. The ambientresistivity determined from the measured insulation resistances, asshown in FIG. 9, is about 1.0×10¹³ Ω·cm for sealing material A, 4.0×10¹⁴Ω·cm for sealing material B, and 4.0×10¹⁵ Ω·cm for sealing material C,respectively. However, these three exemplary sealing material sealedelectrical feedthroughs 100 have 100 MΩ insulation resistance at 260degrees Celsius for sealing material A, 325 degrees Celsius for sealingmaterial B, and 345 degrees Celsius for sealing material C,respectively. By comparing the mechanical stress amplitude, as shown inFIG. 7, an electrical feedthrough 100 sealed with material A, B and Cmay work up to 260 degrees Celsius, 300 degrees Celsius, and 320 degreesCelsius respectively. This combined mechanical and dielectric strengthcould enable such electrical feedthroughs 100 to be operable at least inOil-based wellbores with 30,000 PSI/177 degrees Celsius downholecondition.

Turning now to FIGS. 10-12, the dielectric strength of a sealingmaterial can be measured and to quantify if the sealing materialsatisfies anti-moisture needs. A method for verifying if a dielectricsealing material has moisture resistance may include (i) installing adielectric sealing material sealed feedthrough 100 in a water-basedhydraulic pressurized chamber, (ii) measuring ambient insulationresistance at ambient as reference value, (iii) measuring effectiveinsulation resistance under water-batch soaking process, (iv) measuringeffective insulation resistance under 1-2 hour 100 degrees Celsiuswater-batch soaking process, and (v) measuring effective insulationresistance under elevated temperature and water-based hydraulicpressurized soaking process. The effective insulation resistance may bereadout based on insulation resistance as a function of the 0-600 secondelapsed times. This method is fairly independent of temperature andoften can give some conclusive information on moisture effect on sealingmaterial dielectric properties. Tests by this method are sometimesreferred to as polarization index and dielectric absorption tests.

FIGS. 10 and 11 show two typical effective insulation resistancemeasurements from a ternary B₂O₃—SiO₂—SrO glass system (material D inFIG. 7) in FIG. 10 and a quaternary B₂O₃—Bi₂O₃-MO-REO glass system inFIG. 11, subsequent to soaking in 100 degrees Celsius water for 1-2hours duration. Initial dry ambient insulation resistance from eachsample has first been measured at 500 DCV with the value from 10 TΩ to afew hundred TΩ (or 1 TΩ=1×10¹² Ω). As shown in FIG. 10 that the measuredeffective insulation resistance values from three exemplary feedthroughprototypes have shown a negative exponential function of time. Such atime-decayed IR values strongly indicates unacceptable insulationstrength, especially, the measured dielectric absorption ratio, IR(60)/IR (30) is less than 1.0, implying the sealing material hasunacceptable insulation strength, potentially due to moisture hydroxylion induced surface conductivity at inner surface 18. FIG. 11 providesthe measured effective insulation resistance values from three exemplaryB₂O₃—Bi₂O₃-MO-REO glass system sealed feedthroughs 100 as a function oftime. The data have been fairly fitted to R(t)=R_(o)t^(v) (v=0.1 to0.3). In addition, the measured dielectric absorption ratio,IR(60)/IR(30) is (1.40±0.05), implying the sealing material hasacceptable insulation strength or has desirable moisture-resistantproperties. This power function of the time is consistent with thecapacitance charge response characters, where theτ_(o)=RC≈(3-5)×10⁻¹²*1×10¹⁴≈300-500 sec.

Since the 100 degrees Celsius water soaking process is under atmosphericpressure, it is more likely that the surface of the dielectric sealingmaterial has become conductive due to OH⁻ hydroxyl ion by dipoleinteraction with poled material surface. If assuming a surface layer hasa thickness of h_(s) and surface resistance of R_(s), the effectiveinsulation resistance could be approximately written as

$\begin{matrix}{{R = \frac{R_{v} \cdot R_{s}}{{f_{1}R_{v}} + {f_{2}R_{s}}}},} & (5)\end{matrix}$

where R_(v) is volumetric resistance. f₁ (f₂) is fraction of the surfacelayer (sealing material) thickness over total sealing length, andf₁+f₂=1. It is clear that R could be equal to R_(v) if R_(s)˜∞. On theother case, R<<R_(v) if R_(s)→0, for a highly hydrophilic sealingmaterial. However, if this thin layer of the moisture-rich surface hassurface resistance R_(s) neither infinity nor zero, the effectiveinsulation resistance will degrade as a function of time, as seen inFIG. 10.

To further verify the moisture-resistance from the dielectric sealingmaterial, the electrical feedthrough 100 prototypes have experiencedhydraulic pressurized soaking process up to 30,000 PSI that simulatesdownhole or subsea pressure condition. FIG. 12 provides the measuredinsulation resistances from exemplary Bi₂O₃—B₂O₃-MO-REO sealing materialbased feedthrough 100 prototypes, after 24 hours 30,000 PSI water-basedhydraulic pressurized soaking process. First, all four sealing materialshave also shown positive response as a power function of time, namely,R(t)=R_(o)t^(v) (v is constant). By comparing with ambient insulationresistance values of 50-900 TΩ), the time dependent insulationresistances at least indicate the water or moisture seems to not beaffecting insulation performance after such high hydraulic pressurewater soaking process. Of course, the measurement also found that alayer of white-colored fouling condensed onto the glass surface mayinduce increase in surface conductivity, which can be expected by Eq.(5). Thus, the measured insulation resistance may vary from prototype toprototype because a layer of conductive scaling or fouling that iscondensed onto the sealing material surface that might induce insulationdeterioration. Once again, a polymer material based isolator 31, 36, maybe used as a mechanical barrier to prevent similar fluid that maycontain conductive ions, or salt ions from contacting the dielectricsealing material surfaces of the dielectric seal(s) 21, 26, that providebetter reliability for downhole deployment.

It should be very clear that a moisture-resistant sealing material maynot chemically interact with extrinsic hydroxyl ions or absorb water,but electrical breakdown still may occur because the high hydraulicpressure may force conductive downhole fluid condensed onto the sealingmaterial surface when there exists a differential pressure from oppositesides of a feedthrough 100. The effective insulation resistance can besignificantly reduced by such a conductive surface layer formation.Hydrophobic properties of a dielectric sealing material may alsomitigate water bead up that an electrical feedthrough may be stillnormally function even under the deteriorated insulation. In one case,the effective insulation resistance becomes stable after a certain timeby a balance the moisture inner and outer diffusion from the sealingmaterial surface. In the other case, the water beading up effect at thehydrophobic sealing material surface could suppress further insulationdegradation.

FIG. 13 shows a block diagram of an example method of forming a downholeelectrical feedthrough package (“the method”) 1300 according to variousembodiments described herein. The method 1300 may be used to make afeedthrough package 100 comprising a binary glass system B₂O₃-MO, aternary B₂O₃—Bi₂O₃-MO glass system, or a quaternary B₂O₃—Bi₂O₃-MO-REOglass system with MO=ZnO, BaO, TiO₂, Fe₂O₃ and REO=lanthanum seriesbased rare earth oxide oxides (REO) in which the REO enhanced themoisture resistance by increased hydrophobicity of the glass system. Theuse of REO in the glass system enhances the moisture resistance of theglass system based on the REO in inhibiting hydrogen bonding withinterfacial water molecules resulting in a hydrophobic hydrationstructure.

In some embodiments, the method 1300 may start 1301 and Bi₂O₃, B₂O₃ andMO may be combined to form a glass mixture in step 1302. In furtherembodiments, Bi₂O₃, B₂O₃, and MO may be combined to form a glass mixturein step 1302. In still further embodiments, Bi₂O₃, B₂O₃, MO, and REO maybe combined to form a glass mixture in step 1302. MO may be or compriseZnO, BaO, TiO₂, and Fe₂O₃ or their glass making pre-cursors. REO may beor comprise CeO₂, Y₂O₃, Sc₂O₃, Nd₂O₃, Pr₂O₃, and lanthanum seriesoxides. Preferably, the glass mixture components may be selected by downselecting (as shown in the examples of FIGS. 4 and 5 and Tables 1 and 2)water insoluble glass former(s) and network modifier(s) and controllingeach chemical composition by 20 mol %<Bi₂O₃<60 mol %, 0 mol %<B₂O₃<40mol %, 0 mol %≤(MO)<35 mol %, and 0≤REO<15 mol %.

Next in step 1303, the glass mixture may be heated to approximately650-1400 degrees Celsius. In some embodiments, the glass mixture may beplaced in a suitable container, such as a platinum crucible, and heatedin an electrically heated furnace to a temperature of about 650-1400degrees Celsius depending on the composition. The glass mixture may beplaced in furnace and which allows the melting for the desired time inwhich the glass can be melted properly without any un-melted elementsleft behind. Step 1302 is carried out to allow sufficient meltingtemperature, melting time and preferably intermittent stirring to theglass mixture during melting.

The heated glass mixture may be quenched in a de-ionized water bath toform glass frits in step 1304. In some embodiments, the melted glassmixture may be caste into a container filled with ambient temperaturede-ionized water. Preferably, the glass frits may be ground to have aparticle size of 2-10 μm.

Next, the glass frits may be sintered with a hollow cylinder shape whichcan be fit into a conduit 12 of a metal shell 11 in step 1305. In someembodiments, a metal web 41 may be disposed in the shell conduit 12 andthe glass frits may be sintered with a hollow cylinder shape which canbe fit into the metal web 41 optionally using a burn-off polymer binder.

The sintered glass frits may be positioned in the metal shell 11 and maybe fired at first temperature (T₁) for a first time period to form anelectrical feedthrough assembly (downhole electrical feedthrough 100)having a dielectric seal 21, 26, and to provide a first thermal energyto the dielectric seal in step 1306. In some embodiments, T₁ may bebetween approximately 300-400 degrees Celsius and a first time periodmay be between approximately 30 to 45 minutes.

Next in step 1307, the electrical feedthrough 100 comprising thedielectric seal 21, 26, may be heated at a second temperature (T₂) for asecond time period to provide a second thermal energy to the dielectricseal 21, 26. In some embodiments, T₂ may be between approximately480-650 degrees Celsius and a second time period may be betweenapproximately 20 to 45 minutes.

In step 1308 the electrical feedthrough 100 may be cooled to ambienttemperature for a third time period. In some embodiments, ambienttemperature may be approximately 20-25 degrees Celsius. In furtherembodiments, cooling the dielectric seal 21, 26, in the metal shell 11may be accomplished with a quenching process having a fast cooling rate(η₁) to produce a hydrophobic multi-phase (δ-phase and α-phase) mixeddielectric sealing material so that the third time period may berelatively short and between approximately 0.40 to 0.75 hours. Inalternative embodiments, cooling the dielectric seal 21, 26, in themetal shell 11 may be accomplished with a slow cooling rate (η₂) toproduce a high dielectric and hydrophobic α-phase dominated dielectricsealing material so that the third time period may be relatively longand between approximately 5 to 12 hours.

In step 1309 two isolators 31, 36, may be integrated into the shellconduit 12 so that the dielectric seal 21, 26, is in contact with atleast one of the isolators 31, 36. In some embodiments, integratingpolymer isolator 31, 36, into the shell conduit 12, may includeinjecting a (preferably PAI and/or PEEK thermoplastic) polymer materialinto the shell conduit 12 after glass-to-metal seal fabrication processis completed by injection molding process, including plasticizing,injection, cooling, and ejection from the electrical feedthrough package100. In other embodiments, integrating polymer isolator 31, 36, into theshell conduit 12, may include using “press and shrink fits” to havemachined (preferably PAI and/or PEEK thermoplastic) polymer cylinderwith tiny holes for conducting pin 13 penetration first, and insertingthe polymer cylinder into the shell conduit 12 at a low-temperature(T_(low)=−60 degrees Celsius) controlled environment chamber. Since thisinjection molding is following the glass-to-metal seal process, thethermoplastic isolators 31, 36, have an amount compression provided bythe CTE mismatch between Inconel metal shell 11 and polymer material atelevated temperature. After step 1309, the method 1300 may finish 1310.

Although the present invention has been illustrated and described hereinwith reference to preferred embodiments and specific examples thereof,it will be readily apparent to those of ordinary skill in the art thatother embodiments and examples may perform similar functions and/orachieve like results. All such equivalent embodiments and examples arewithin the spirit and scope of the present invention, are contemplatedthereby, and are intended to be covered by the following claims.

What is claimed is:
 1. A method of forming a downhole electricalfeedthrough package, the method comprising: combining at least two ofthe four components selected from Bi₂O₃, B₂O₃, MO, and optionally REO toform a glass mixture; heating the glass mixture to approximately 650 to1400 degrees Celsius; quenching the heated glass mixture in de-ionizedwater bath to form glass frits; sintering the glass frits with hollowcylinder shape and fitted into a conduit of a metal shell to form anelectrical feedthrough assembly; firing the electrical feedthroughassembly at first temperature (T₁) for a first time period to form adielectric seal and to provide a first thermal energy to the dielectricseal; heating the electrical feedthrough assembly at second temperature(T₂) for a second time period to provide a second thermal energy to thedielectric seal; cooling the dielectric seal of the electricalfeedthrough assembly to ambient temperature for a third time period; andintegrating two isolators into the conduit so that the dielectric sealis in contact with at least one of the isolators.
 2. The method of claim1, wherein B₂O₃ is between 0 mol % to 40 mol %.
 3. The method of claim1, wherein MO is selected from the group consisting of ZnO, BaO, TiO₂,Fe₂O₃, and their glass making pre-cursors.
 4. The method of claim 1,wherein MO is between 0 mol % to 35 mol %.
 5. The method of claim 1,wherein Bi₂O₃ is combined with B₂O₃ and MO to form the glass mixture,and wherein Bi₂O₃ is between 20 to 60 mol %.
 6. The method of claim 4,wherein a REO is combined with B₂O₃ and MO to form the glass mixture. 7.The method of claim 5, wherein REO is selected from the group consistingof CeO₂, Y₂O₃, Sc₂O₃, Nd₂O₃, Pr₂O₃, and lanthanum series oxides.
 8. Themethod of claim 5, wherein REO is between 0 mol % to 15 mol %.
 9. Themethod of claim 1, wherein the first temperature (T₁) is approximately300 to 400 degrees Celsius and the first time period is approximately 30to 45 minutes, and wherein the second temperature (T₂) is approximately480 to 650 degrees Celsius and the second time period is approximatelyfrom 20 to 45 minutes.
 10. The method of claim 1, wherein cooling thedielectric seal in the metal shell is cooled with a quenching process toproduce a hydrophobic multi-phase (δ-phase and α-phase) mixed dielectricsealing material.
 11. The method of claim 1, wherein cooling thedielectric seal in the metal shell is heated approximately 480 to 550degrees Celsius and cooled for approximately 5 to 12 hours to produce ahigh dielectric and hydrophobic a-phase dominated dielectric sealingmaterial.